Major tech MT350 User manual

INSTRUCTION MANUAL
LOOP IMPEDANCE & PSC TESTER
MT350

Contents Page no
1. Safety Information.............................................................................3
2. Safety Symbols..................................................................................3
3. Operating Instructions.......................................................................3
3.1. Voltage Test............................................................................3
3.2. Loop Test................................................................................4
3.3. Prospective Short Current Test...................................................4
4. Features...........................................................................................4
5. Electrical Specifications......................................................................5
5.1. Loop Resistance.......................................................................5
5.2. Prospective Short Current.........................................................5
5.3. AC Voltage (50Hz)....................................................................5
6. Parts & Controls................................................................................5
7. Measurement of Loop Impedance and Prospective Short Current............6
8. Battery Replacement.........................................................................7
2

1. SAFETY INFORMATION
• Read the following safety information carefully before attempting to
operate or service the meter.
• To avoid damages to the instrument do not apply the signals which
exceed the maximum limits shown in the technical specifications tables.
• Do not use the meter or test leads if they look damaged. Use extreme
caution when working around bare conductors or bus bars.
• Accidental contact with the conductor could result in electric shock.
• Use the meter only as specified in this manual; otherwise, the protection
provided by the meter may be impaired.
• Read the operating instructions before use and follow all safety
Information.
2. SAFETY SYMBOLS
Caution refer to this manual before using the meter.
Dangerous voltages.
Meter is protected throughout by double insulation or reinforced
insulation.
When servicing, use only specified replacement parts.
CE Comply with EN-61010-1
3. OPERATING INSTRUCTIONS
Link the test line
Check the wires state:
Before pushing the "test" button, certificate the 3 led status
P-E - led light
P-N - led light
P-N - reverse led not light
If indicating light's status is not like this, don't test and check the
wires again.
3.1. Voltage test
When the tester is linked to the power, LCD will update the voltage (P-E)
per second. If the voltage is unusual or not expected value, don't proceed
with the test!
The tester only used in AC230V +10% -15% (50Hz).
3

3.2. Loop test
Turn the tester to 20, 200 or 2000Ω range. Push the test button, LCD will
display the value and unit, the tester will beep once after the test is over.
To get better value turn the tester to lower range as possible. If LCD flash
" " , disconnect the tester and power and make the tester cool down.
3.3. Prospective short current test
Turn the tester to 200A, 2000A or 20kA range. Push the test button, LCD
will display the value and unit, the tester will beep once after the test is
over.
To get better value set the tester to lower range as possible. If LCD flash
" " , disconnect the tester and power and make the tester cool down.
4. FEATURES
Lines test 3 LED indicates lines state. When reversed, the
third LED lights up.
Over heat protect When the temperature of the resister is high,
the tester will cut and lock. LCD will display
"Temperature is High" and flash the flag " "
Overload protect When the volt of P-E is up to 250V, the tester
will stop test to protect the tester and LCD will
flash "250V”
Low Battery Indication The flag " " is displayed when the battery
voltage drop below the operating voltage.
Test mode When you press the key "test", tester will
display the result for 5's then display the
voltage.
Operating Temperature 0°C to 40°C (32°F to 104°F) and Humidity
below 80% RH
Storage Temperature -10°C to 60°C (14°F to 140°F) and Humidity
below 70% RH
Power source 6 x AA batteries
Dimensions 200(L) x 92(W) x 50(H) mm
Weight Approx 700g including battery .
Function Range
4

5. ELECTRICAL SPECIFICATIONS
Accuracies are specified in the way:
± (…% of reading +…digits) at 23°C ± 5°C,below 80% RH.
5.1. LOOP RESISTANCE
Range Resolution Test Time Full Scale Accuracy
20Ω 0.01Ω 25A/20ms ± 2% of F.S ± 5d
200Ω 0.1Ω 2.3A/20ms ± 2% of F.S ± 5%
2000Ω 1Ω 15mA/20ms ± 2% of F.S ± 5d
5.2. PROSPECTIVE SHORT CURRENT
Range Resolution Test Time Full Scale Accuracy
200A 0.1A 2.3A/20ms ± 2% of F.S ± 5d
2KA 1A 25A/20ms ± 2% of F.S ± 5d
20KA 10A 25A/20ms ± 2% of F.S ± 5d
Range Full Scale Accuracy
50~255V ± 2% of F.S ± 5d
5.3. AC VOLTAGE (50HZ)
6. PARTS & CONTROLS
1. Digital Display
2. Backlight Button
3. P-E,P-N,Lights
4. P-N REVERSE Light
5. Test Button
6. Rotary Function switch
7. POWER Jack
8. Pothook
9. Battery Cover
5

7. MEASUREMENT OF LOOP IMPEDANCE AND PROSPECTIVE
SHORT CURRENT
If there is a RCD or fuse in the circuit, they must be bridged out prior to
testing the loop impedance.
According to IEC 60364, every loop should meet the formula: Ra≤50/la
Ra: loop impedance
50: max of touch voltage
Ia: the current than can make the protection device break down the circuit
in 5 seconds.
When protection device is RCD, Ia is rated residual current IΔn.
IΔn 10 30 100 300 500 1000 mA
Ia(50v) 5000 1667 500 167 100 50 Ω
Ia(25v) 2500 833 250 83 50 25 Ω
According to IEC 60364, every loop should meet the formula: Zs ≤ Uо/la
When protection device is FUSE, Uо=230V, la and Zsmax:
Rated Break time (5s) Break time (0.4s)
Current Ia(A) Zs(Ω) Ia(A) Zs(Ω)
6 28 8.2 47 4.9
10 46 5 82 2.8
16 65 3.6 110 2.1
20 85 2.7 147 1.56
25 110 2.1 183 1.25
32 150 1.53 275 0.83
40 190 1.21 320 0.72
50 250 0.92 470 0.49
63 320 0.71 550 0.42
80 425 0.54 840 0.27
100 580 0.39 1020 0.22
Prospective short current must be bigger than la.
6

8. BATTERY REPLACEMENT
1. When the low battery symbol " " appears on the LCD, the six 1.5V 'AA'
batteries must be replaced.
2. Turn the meter off and remove the test leads
3. Unsnap the tilt stand from the rear of the meter
4. Remove the four Phillips head screws holding the battery cover
5. Remove the battery compartment cover
6. Replace the batteries observing polarity
7. Affix the rear cover and secure the screws.
8. Reattach the tilt stand
7

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